[QUOTE=Supercharged FC;10169905]So here's my map. I'm not near the surge line especially at high RPM were my issue occurred. (See circle) I was running a T04E 57 trim with a 1 A/R turbine housing. [QUOTE]

Oops here a pic that works (hopefully)

https://www.rx7club.com/attachment.p...1&d=1282185618


[Quote=Slides;10170638]
Logic fail.

If the BOV is hooked up in the conventional fashion diaphragm reference post throttle and the throttle sticks the BOV will not open, [Quote]

I did not think I had to explain this.....
If your throttle is stuck open so much you don't have vacuum it would not matter if you had a turbo or not your engine would accelerate. I always had vacuum in my manifold when I let off the throttle.

Throttle plate are not a perfect seal, my plates where held open about 1/4 inch when they stuck.

If it happen to me it could happen to someone else.

I've had the same Garrett, plain bearing, non water cooled, turbo on my engine, *without* a BOV for 140 000ks (85 000+mls) running 15psi and it is just as tight, with no slop in the bearing today as it was when I bought it.

You better put one on now you're hurting the longevity of your turbo!

...wait:scratch:

no wait. you need more proof then that. Some people are very thick.

ha so tonight I was out cruising in the 7 with this hot blonde. She had never been in it before. When I shifted or let off the throttle she would make little fluttering sounds and say "I love the sound effects!" She didn't even know or ask what kind of car she was in or what was making the sounds...

I took another friend out in the 7 a couple nights ago. He's not a hardcore car guy but he's got a mildly modified 90s turbo Volvo. He asked me "Where can I get that blowoff valve???" I told him I didn't have one and he was incredulous. "Wait... so how did you get that super sequential sound?" I said "The air comes back out the inlet of the turbo and it makes that sound." The conversation left him a little confused.

Pics of the blonde or it didn't happen!

Attachment 711135
This mod gets the Hot Blonde® seal of approval

Manlaw confirmed!

Aw your telling me the hot blonde didnt know the difference between mad tyte jdm wheels or some sportmax/rotas...lol

This thread just won!

so i look at it this way and hear me out. Now i know diesels have no thottle plate/throttle body ect... but i have worked on some high horse and stock diesel trucks with a intake on them and i can tell u that when u horse around on them and let off after full boost yea can hear the flutter from the turbo and its actually easier to get the effect on a manual. I have seen some 700hp cummins twist two small shaft turbo's from the back spool and that just from the shock from the instant back spool of 50 psi lol. So the customer put a large shaft turbo in the truck and everything is fine now. But where i am getting at is these trucks are not having any problems so far, And there are tons of diesels out there with no problems with back spool

Trots I'm starting to see a growing trend, anytime pics or blondes comes up you're all over it!! It was a nice change of pace today in class though, when I was scrolling through this thread, I did the 'double scroll' I guess we'd call it, scrolling down to the last post and then you wonder what picture just went shooting up your screen...I scrolled up, and I probably will after posting this.

...back on topic

If the blonde likes it then we all should do it.

Come to the lounge now and Pm us some of the good pics of her :)

Youtube video showing the compressor wheel of a turbo with no blowoff valve as the throttle is released.

http://www.youtube.com/watch?v=mciE5...eature=related

so apparently "dosing" is a term for running without a BOV, a "dose pipe" is a turbo inlet pipe on a turbo without a BOV, and a "dose" is a high pitched flutter.

And here is a video of "true compressor surge" under WOT (not when letting off the throttle) on a Skyline

http://www.youtube.com/watch?v=nCj6Spwl1CU

At about 1:00 on this video you can see the horsepower and boost pressure oscillating like crazy. It looks like they are operating the brake to hold 4000rpm (look in the upper left corner, you can barely see it). Under those conditions it has pushed the turbo out of its efficiency range.

[QUOTE=arghx;10187568]Youtube video showing the compressor wheel of a turbo with no blowoff valve as the throttle is released.

And here is a video of "true compressor surge" under WOT (not when letting off the throttle) on a Skyline

[QUOTE]

Thanks for the videos. It's hard to explain compressor surge without people thinking of engine surging.

http://www.youtube.com/watch?v=11ksv...eature=related
here is a turbo about to blow up lol!!!!! See turbos can handle this

/\ /\ /\ = I ran 3 years at 30psi held (about 25-30k hard miles or so) with no BOV and no worries on a T3/4.

^^Im with you on that one Supercharged, unless someone can show the numbers to back it up, dont believe it.
CBR now uses a BOV on his race car, after having told me not to other with them (I fitted one anyway).
The theory behind a bov make a lot of sence, so unless actual test show they arent needed, and so long as every factory turbo car i have seen under the bonnet of uses one, ill use one on my street car.

Its a bit different with a car that doesnt usualy close the throttle until the end of a run down the track

Arghx, do you have any notes from BW on their development of the EFR turbos, specifically why they chose to run an incorporated BOV?

I alluded to this in the other EFR turbo thread. So, does this look familiar?

https://www.rx7club.com/attachment.p...1&d=1289955369

Sorry, I am pretty dense. What does it resemble?

Well I'm upto 22 months with no bov. The original turbo with probably 20 of those months is on my shelf. No thrust play. Side to side feels normal.

My question is, if I want to BOV. Not because I need to. How do I get the bugger to seal underload unconditionally but also open on light lifts that induce surge with a small T3/T4 size turbo.

Light spring.

The only limitation is you have to work out the diaphram to underside (ie intake pipe sealing face) piston ratio if it isn't 1:1 & to compensate for intercooler pressure loss if it is before the intercooler (for it to hold shut WOT) as the post throttle pressure could be 2-6psi less than pre intercooler.

If it is just in front of the throttle you should be able to get away with a half pound spring.

Else if you have a sealed unajustable unit, I guess you would go the other way and run it just after the compressor so that the pressure differential was greatest post throttle vac ref vs compressor outlet provided it wasn't leaking on load, i guess you could tape a whistle to it or something to make sure it wasn't leaking at peak load.

That's the factory recirculation valve/diverter valve/blowoff valve on a VW/Audi 2.0T engine. The turbo is made by BorgWarner and the recirculation valve is pretty similar to what the EFR turbos have. You can see this one for the 2.0T uses electronic actuation like Ford Ecoboost recirculation valves, but BW has had the pneumatic design (similar to what's on the EFR) for longer. The BW EFR turbos are using recycled designs from 6+ years ago. Just like there's nothing new about a twin scroll inlet with dual internal wastegate passages.

As for the efficacy of the design, well I don't have any lab tests. It seems to me though that it would be the best air bypass valve design because it is relieving pressure right before the compressor wheel so the wheel won't brake as much. In my mind if you are going to have a blowoff valve this style of integrated recirculation would be the best one to have.

BMW has the best design though because they go around the problem altogether. The N54 twin turbo engines do have more traditionally designed recirculation valves but they actually keep the throttle open during shifts. Yeah, you heard me, they don't close the throttle between shifts.

https://www.rx7club.com/attachment.p...1&d=1289964622

The BMW N55 engines don't have a throttle valve at all. Gasoline direct injected engines don't need throttles. In 5 to 10 years there will be very few gasoline engines with throttles. Mazda has had unthrottled direct injected rotary engines in labs for decades.

At this stage. I'm going to call my intercooler pressure drop .14bar 2psi @ 5000rpm, .3bar at 7000rpm. The known error is a spring that assumes 1:1 EMP:IMP.

Expected high exhaust manifold pressure.

IAT sourced in air pipe is 45degC after 3 gears @100% throttle, from a steady state of 30degC cruising.


So slides, an engineer would make a BOV with a larger diaphram surface area than piston surface area, to remove the problem is blowing open?

I got you now Arghx. It certainly isn't uncommon for the aftermarket to hype up "new" products that are lightyears behind the OEM, just look at our selection of fuel injectors.

The no-throttle DI engines are pretty neat.

A big part of theproblem with aftermarket parts is they are designed for a broad range of vehicles etc. The computer logic and processing horsepower necessary to make new systems like DI, with twin independent VCT, variable lift, etc require countless engineering hours, engine dyno mapping, DOE and lots of computer modeling just to control, and all of this with proprietary software and hardware. This is affordable by an OEM becuase they spread the development cost over thousands/millions of vehicles. To get to an OEM level on a single custom vehicle it would literlaly cost you millions of dollars.... I always think it is funny when an aftermarket "chip" company or whatever claims to be better than OEM.. maybe in one aspect but as with everything there are tradeoffs...

pointless rant over...

Yes I agree Direct injection is very cool, there are many things you can do with DI that are not possible with port injection, like use fuel as knock control without going pig rich, multiple injections per cycle, near instant response...

Yes, or rather, throw it in the bin :lol:, or experiment with intake side boost control if it was a roller bearing turbo & space was tight.

I could have easily done intake side boost control. In fact it would have been easier not harder. I heard the argument 'do/did formula 1 cars use it' and then decided it was flawed.

"true compressor surge" Both of those videos actually show compressor surge, one however is more damaging than the other due to load on the turbine being greater.

~S~

on MAP based cars the MAP sensor is constantly reading your intake pressure past the throttle body, so any residual pressure in the system or passing the throttle body is already being compensated for.

^ Also, detonation can't happen without fuel. Injectors being shut off != less fuel, its equal to no fuel. When injectors shut off, its not like they shut off mid duty, they only stop injecting next cycle so the previous cycle has the correct amount of fuel and the following cycle has none.

thewird

sooo, im kinda reviving this..

I dont know if i believe no bov is better than a bov but, it seems like its mythical. id run a bov just because thats whats familiar to me. BUT i dont have one at the moment and my car is almost about done. I have to break in my motor so i wont really see boost so will i be okay if i drive around a few miles without a BOV? (remember i wont be going into boost)

It will be fine, especially because you are not boosting and because the FD doesn't have a MAF sensor. I've been going 2 years without one now.

5 Years and multiple cars for me

Just a little thanks for reviving the thread so I saw it and read through it. Thanks to arghx for being a guinea pig and keeping us up to date on his adventure. Kinda nice to get to the end and see it doesn't really matter.

good read... take it for what its worth http://www.autospeed.com/cms/article...estions&A=1457

Real simple, if you can shift very quickly without lifting you don't need a bov. If you need to lift & your shifts are not as quick as an F1 then a bov is needed to stop turbo surge & damage to internal bearings, etc.

It might not happen in 1 day but turbo failure will eventually occur. It is not for emissions, horsepower increase, or mythical sales figures, these are facts. In order to keep the turbocharger spinning while in between shifts or in neutral after it has been in boost, pressure needs to be released if a throttle body is present. This is a fact!

If that is the case, why in the fuck when people actually ran bush/thrust bearing turbos with post turbo throttles without ignition retard or cut/fuel cut shifts in endurance race cars running much lower trim large diameter high PR setups in teams with massive budgets did they not use these valves?

So have you instrumented even one car with turbo tacho, pre throttle pressure sensor and such and actually logged what happens?

Pressure pre-throttle rises very slightly, but being a centrifugal compressor, unless you have run it into choke, it will only support around the same pressure ratio (and when flow reduces into the turbo there is less intake depression and hence a slight increase post turbo as PR stays the same) at any given rpm regarless of flow rate until if falls into surge.

Turbos don't turn backwards & shaft/compressor interface loading is much higher on load. The only issue you might have with a bush/thrust turbo with very loose tolerances is axial vibration.

Given so many of the BOV alarmists actually want their cars setup with ignition cut rev limits or 2 steps i find it hilarious as if anything is going to overload the turbo bearings, ignition events in the exhaust manifold will.

Fucking retards

Compressor surge:

The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side.
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself.
Common conditions that result in compressor surge on turbocharger gasoline engines are:

* A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
* The outlet plumbing for the bypass valve is too small or restrictive
* The turbo is too big for the application

Interesting to read that from someone with a forum name of 97SupraTwinTurbo, an engine that was engineered to compressor surge under full load right off the showroom floor (with a warranty!). That's what happens to the No. 2 turbo on the 2JZ when the intake air control valve and reed valve are shut during prespool. The Rx-7 and Cosmo also compressor surge under full load; Mazda has provided detailed documentation on this. It helps improve spool of the No. 2 turbo. I have the documents to prove it; see https://www.rx7club.com/3rd-generation-specific-1993-2002-16/comparison-rx-7-13b-rew-supra-2jz-gte-sequential-turbos-960727/ and I can also email them to you. A turbo can withstand sustained compressor surge under full load for a limited time without damaging anything; both Mazda and Toyota used that principle in the design of their sequential turbo systems.

https://www.rx7club.com/attachment.p...1&d=1292018297

As I've said in this thread all along, I don't fully have a dog in this fight. I wouldn't say I'm for or against air bypass valves and I've run with and without them. But deleting a blowoff/bypass valve isn't going to blow up your turbo, not in this kind of application. I don't consider the compressor wheel stalling under deceleration as 'true' compressor surge, because there are basically no exhaust gases driving the turbine. The main thing that affects the speed of the compressor wheel between shifts is the bearing design; we all know that ball-bearing turbo maintains compressor speed much better.

This was a good read haha!

There is a massive difference between a couple of tut tuts on throttle off with no exhaust energy and running 30-40% of full power exhaust flow energy into a loaded compressor with a missmatched cold/hot side combination when it comes on in the midrange. As evidenced by the fact that manufacturers are still using parallel sequential systems, you have to run the secondary turbo in surge up to a point so that when it is allowed to flow it has the wheel speed to sustain the pressure in the intake system.

I love how people with no experience of it will tell people with countless years of exeprience that they are wrong and a load of cut n paste 2nd hand info is their proof.

Theory and reality are very different.

Ive got first hand experience of the reality, about 10 years worth, countless cars, inc a 23psi rotary, a 25psi old pushrod blow thru beasty, and a 30psi 4pot, all used hard on roads and circuits too, not a few quick runs up a strip, and I know what breaks and what doesnt. Dont think 10yrs worth counts as me being 'lucky'

Im not jumping on either side of the fence here. I currently live in Okinawa Japan and I drive a JZ100 Chaser with a single turbo 1jz. I dont have a blow off valve and its been that way since the previous owner. Its a common thing here on island for the locals to run with no blow off valves. Car still pulls strong.

Interesting!

My first car was an '88 Chrysler Conquest TSi. Stock it didn't have a BOV, nor did it recirculate to the best of my knowledge. Extra pressure just went backwards through the turbo / intake. I really do miss the ol' compressor "surge" sound. Hell of a fun car, and damn quick too. Did end up replacing the turbo at ~98k miles, though its failure was due to a cracked oil line.

Ive been running no Bov on my Greddy T78 setup for over a year now, the turbos response is very quick between shifts and is showing no adverse effects..

shoot i think i will try this

Arghx, thank you for posting this up and experimenting, along with the others who are doing it. I am in the process of upgrading my intercooler and piping. With my current setup I am getting "surge" at low boost since my BOV can't respond to my low vacuum. I have been running like this for 2 years. I was actually going to try to cure this by using a synapse valve. Thanks to this thread I can save that BOV money and get some new injectors while cleaning the engine bay up even more!

Only problem is I think I am a ricer since I have a "dose" pipe! My intake runs to the nose of the car.

http://youtu.be/JUGOkyJbJpw

Very informative thread. Looks like I'll be saving a lil more money by not buying a BOV for my build.